Spray nozzles for atomizing liquid with a pressurized gas such as air are known in the art. For example, the liquid is sometimes broken up mechanically and by pressurized air in an atomizing chamber located upstream of the spray nozzle. The atomized liquid is then ejected from the nozzle through one or more discharge openings formed at the distal end of the nozzle.
An often-sought goal in atomizing and spraying apparatus is to achieve high efficiency. High efficiency in the context of this invention refers to using as little air energy as possible to break liquid of a given volume into particles having a relatively large total surface area. Larger surface areas are created by breaking the liquid into very fine particles.
A further goal is to provide nozzles having the capability of discharging the liquid in different spray patterns. By way of example, some applications require a narrow angle round spray, other applications may require a wide angle spray such as a full cone spray. Still other applications may require a flat spray.
In prior atomizing/spraying apparatus, the desired spray pattern is usually generated by forcing the atomized liquid through a properly shaped discharge orifice construction disposed in the nozzle. A narrow angle round spray, for example, may be created by providing the nozzle with a single round orifice. A wide angle round spray pattern may be generated by a nozzle having a plurality of angularly spaced diverging orifices. An elongated slot or an elliptically shaped orifice in the discharge nozzle produces a substantially flat spray pattern.
Nozzles having discharge orifices of the above type are essentially passive with respect to effecting further atomization of the liquid as the liquid is discharged from the nozzle. Certain nozzles produce further atomization during flow of the liquid through the nozzle, however, for the most part, the atomization effected by the nozzle has limited impact on the overall efficiency of the atomizing and spraying apparatus. In addition, these nozzles fail to produce a relatively constant spray angle over a varying range of applied air pressures.